How to get previous and new selected value from a option DOM element with JavaScript?

Question

How can I retrieve the new selected value and the previous selected value with JavaScript when onChange or similar event is called?

<select size="1" id="x" onchange="doSomething()">
  <option value="47">Value 47</option>
  ...


function doSomething() {
  var oldValue = null; // how to get the old value?
  var newValue = document.getElementById('x').selected.value;
  // ...

Thank you! :)

Answer 1

Look here: Getting value of select (dropdown) before change I think the better,

(function () {
    var previous;

    $("select").focus(function () {
        // Store the current value on focus, before it changes
        previous = this.value;
    }).change(function() {
        // Do something with the previous value after the change
        alert(previous);
    });
})();

Answer 2

Below worked for me. Add below two events to your select HTML tag:-

onFocus='this.oldValue = this.value'; //if required in your case add this line to other events like onKeyPressDown and onClick. 
onChange = 'alert(this.oldValue); this.value=this.oldValue'